The present invention relates to a partially or fully cured thermosetting product. The cured product comprises a molded and cured thermosetting composition which is the reaction product of at least one monomeric or polymeric thermosetting resin and at least one toughening agent having at least one primary or secondary reactive function. The toughening agent comprises at least one hyperbranched dendritic macromolecule substantially built up from ester or polyester units, optionally in combination with ether or polyether units. The hyperbranched dendritic macromolecule is composed of a monomeric or polymeric nucleus to which a number of branching generations are added, said branching generations comprising at least one branching chain extender having three reactive functions. The reactive functions of said branching chain extender are at least one hydroxyl and at least one carboxyl group.
Molded thermosetting materials can be classified in many ways depending on the identified concept. For example, molded thermosetting materials include those with or without reinforcement, and include engineering plastics, laminates, sheet molded sandwich structures and other composite structures. A composite is, in general, classified as a material deriving its properties from two or more components which can be distinguished readily when examined under optical or electron microscopes. The strength and toughness of, for instance, engineering plastics are achieved by combining high strength phases, such as various fibers or particles, and a ductile phase, such as a resin or a resin composition. Molded thermosetting materials are used in a wide variety of applications, which applications require specific properties obtained from included components. The versatility of material property design and processing possibilities obtained by using molded thermosetting materials has been and will remain a major driving force for their use. However, certain drawbacks still remain. Among these are properties related to mechanical anisotropy and also to their relatively high processing costs. Mechanical properties are mainly influenced by properties, such as the toughness, of the cured or semi-cured resin or resin composition. Some important applications areas of molded thermosetting materials and the main requirements for further mechanical improvements are listed in summary below.
______________________________________ PROPERTIES IN NEED TYPE OF PRODUCT OF IMPROVEMENT ______________________________________ Aeronautic goods and Impact properties, damage articles tolerance Nautic goods and articles Moisture absorption, impact Chemicals/chemical goods Chemical resistance, notch and articles sensitivity Automotive goods and Low velocity impact, fatigue articles tolerance Sporting goods and Fatigue, impact, low articles velocity impact Leisure/commodity goods Damage tolerance, low and articles velocity impact Electric/electronic goods Thermal shock resistance and articles ______________________________________
The toughness of a cured or semi-cured resin or resin composition is one of the most important intrinsic properties of a molded thermosetting material, such as a laminate, a sandwich structure, a composite or the like, controlling various observable damages and failure mechanisms. Important mechanical properties and failure mechanisms can be summarized:
The fatigue properties are controlled by the rate of crack growth through the material dependent of the inherent toughness and durability of said resin or resin composition and interfaces.
The impact properties are characterized by the energy absorbed, the damage area and the residual strength after impact. The toughness of said resin or resin composition limits the extent of damage thus allowing good residual strength.
The low velocity impact property is the resistance to small impacts due to mishandling, such as dropping and stone hitting (important in automotive applications). The extent of damage is mainly controlled by the toughness of said resin or resin composition and adhesive properties.
The damage tolerance and notch sensitivity are related to the presence of defects. These can originate from low velocity impacts, machining or production defaults. The further cracking of for instance a laminate, a sandwich material or other composite structures will involve cracking by traverse cracking (predominantly in 90.degree. oriented plies) and delamination. Toughness is thus a major controlling parameter.
The toughness of said resin or resin composition is also important in controlling the edge effects of parts of said molded materials and the thermal loading inducing delamination. The prolongation of delamination may induce interfacial failures.
The resin or resin composition has been shown to play an important role in the performance of for instance fibrous materials. This is disclosed in "The Role of the Polymeric Matrix in the Processing and Structural Properties of Composite Materials", J. C. Seferis and L. Nicolais, Plenum Press, New York, 1983. The resin or resin composition will not just control the maximum service temperature, due to its glass transition, but also moisture sensitivity and aging properties of the cured or semi-cured molded material. Furthermore, defects induced during processing can often be avoided by adjusting and controlling resin viscosity and fiber or particle wetting characteristics. The anisotropic nature of molded materials further emphasizes the importance of the mechanical properties of the cured or semi-cured resin or resin composition. Interlamilar properties are mainly affected, as are intralamilar properties, where low level damage propagation occurs through cracking. Therefore, the properties of the resin or resin composition are of primary interest in the development of new thermosetting molded materials.
The toughness of said resin or resin composition is important when considering damage initiation and fracture of said molded materials. It will affect properties such as the interlamilar crack resistance, impact energy absorption, damage propagation and fatigue resistance. These are often limiting characteristics for the materials in high performance applications. Reinforced epoxy materials are, for instance, widely used as structural load bearing elements where low toughness properties will affect the durability of the material and impose severe limits on design parameters. Toughness implies energy absorption before failure occurs. The energy absorption at a crack front can be achieved through various deformation mechanisms, as for instance disclosed in "Sources of Toughness in Modified Epoxies", R. A. Pearson, Ph.D. thesis, University of Michigan, 1990, which are most effectively induced by the presence of a second phase in the form of particles. The secondary phase is often introduced in the form of rubber particles which normally leads to a considerable increase in the resin viscosity.
The plastic strain to failure can be increased by reduction of the crosslink density or the use of plasticizers. This, however, will very strongly affect the modulus and thermal properties of the material, only giving a moderate increase in toughness. The toughness can effectively be increased by addition of a toughening agent, such as said particles. The effect of particle toughening will, regardless of the nature of the particle, depend on the particle size, interparticle distance and volume fraction. Toughening particles include glass particles, rubber particles and thermoplastic particles having either a rigid core and a soft shell or a soft core and a rigid shell structure. These particles can have different adhesive properties to the surrounding resin or resin composition, which affect their toughening effect and influence the modulus of said resin or resin composition. Toughening systems can furthermore include phase separation during curing. A dispersed spherical phase is usually created in such a process.
Today commonly used toughening agents include rubber, carboxyl terminated butadiene acrylonitrile (CTBN rubber), latex and short reactive thermoplastic chains such as polyetherimides. CTBN rubber is the most effective and most widely used toughening agent. However, it very strongly affects the thermal and mechanical properties in the resin matrix. A combination of CTBN rubber and glass particles reduces the negative effect on the mechanical properties. Polyetherimide modifiers are most recently developed systems. These systems do not affect the thermal and mechanical properties of the matrix, but are less effective as toughening agents.
Processing techniques for reinforced molded materials often involve a wetting stage of a reinforcing bed. The wetting is most often done using a resin in liquid state thus requiring a controlled viscosity. The viscosity should be low in order to obtain a good penetration of for instance a fiber bed, a proper wetting of the fibers and a reduced wetting time. Toughened resins or resin compositions as disclosed above generally exhibit increased viscosity and toughening particles are often too large to be able to freely penetrate the reinforcing bed. As a consequence, in processing techniques producing superior quality molded thermosetting materials or allowing products having a complex geometry to be produced at high productivity rates, particles will be subject to segregation, percolation or shear field segregation. The effect of such toughening agents will therefore strongly be reduced and can even become a source of weak spots if they agglomerate to a large extent. This kind of processing include lamination, prepreging and/or impregnation techniques, such as infusion, compression transfer, vacuum molding, transfer molding, injection molding, gas assisted injection molding, structural injection molding, filament winding, resin immersion, resin infusion, press molding and vacuum molding. Further processing techniques include die forming such as extrusion, rotary molding, gravity molding, blow molding, casting and pour molding. Thus, the quality of the impregnation will decrease and processing times increase and even the quality of the final product may decrease. This is of course very much dependent on the particle size and to a lesser extent the particle volume fraction. The toughening effect of smaller particles is not optimal. Larger particles can be applied using an interleaf layer between plies of a sandwich structure or other composite material. This will increase the toughness of the interlamilar region where delamination occurs, but will not increase the toughness within the plies. CTBN rubber strongly increases the resin viscosity thus limiting the volume fraction that can be used.
Through the present invention is possible to produce a molded thermosetting product, wherein the thermosetting resin has increased toughness properties without, or only slightly affecting processability, thermal and other mechanical properties. The thermosetting product comprises a toughening agent, which toughening agent is a hyperbranched dendritic macromolecule built up from ester or polyester units, optionally in combination with ether or polyether units. The toughening properties of said macromolecule are excellent and most important, toughening can be obtained without imparting the modulus or the thermal properties of the thermosetting resin or resin composition included in the resultant thermosetting product.
Hyperbranched dendritic macromolecules, including dendrimers, can generally be described as three dimensional highly branched molecules having a treelike structure. Dendrimers are highly symmetric, while similar macromolecules designated as dendritic or hyperbranched may to a certain degree hold an asymmetry, yet maintaining the highly branched treelike structure. Dendrimers are monodisperse or substantially monodisperse hyperbranched dendritic macromolecules. Hyperbranched dendritic macromolecules normally consist of an initiator or nucleus having one or more reactive sites and a number of branching layers and optionally one or more spacing layers and/or a layer of chain terminating molecules. Continued replication of branching layers normally yields increased branch multiplicity and, where applicable or desired, increased number of terminal functions or sites. The layers are usually called generations and the branches dendrons. Hyperbranched dendritic macromolecules can be illustrated by below simplified Formulas (I) and (II) wherein X and Y are initiators or nuclei having four and two reactive sites, respectively, and A, B and C are branching chain extenders having three (A and C) and four (B) reactive sites, each branching chain extender forming one branching generation in the macromolecule. T is a terminating chain stopper or a suitable terminal function or site, such a hydroxyl, a carboxyl or an epoxide group. The hyperbranched dendritic macromolecule of Formula (I) holds four equal and the macromolecule of Formula (II) two equal so called dendrons linked to respective nucleus. The dendrons of the macromolecule of Formula (I) is as disclosed by simplified Formula (III). A dendron can be pre-produced, and then added to a nucleus, by for instance condensing one or more hydroxyfunctional carboxylic acids, by allowing mono, di, tri or polyfunctional carboxylic acids to form esterlinks with mono, di, tri or polyfunctional alcohols or epoxides or by similar procedures resulting in esterlinks, etherlinks or other chemical bonds. The raw materials used to produce a dendron must be chosen to provide at least one terminal function reactable to a nucleus or initiator.
Hyperbranched dendritic macromolecules are not yet in all respects fully characterized and are distinguished from the well-known ordinary linear or branched molecules or macromolecules and likewise distinguished from the likewise well-known so called star or starbranched molecules and macromolecules. Hyperbranched dendritic macromolecules as disclosed by Formula (I) and (II) can by no means be compared with said well-known molecules, neither in regard of molecular structure nor in regard of chemical and/or physical properties. Increased branch replication in a hyperbranched dendritic macromolecule yields increased branch density and if desired increased number of terminal functions or sites, neither, of these distinguishing properties are exhibited by said well-known and ordinary molecules. Increased branch replication in a star or starbranched molecule or macromolecule does neither yield said increased branch density nor said increased number of terminal functions or sites. A star or starbranched macromolecule can be illustrated by below simplified Formula (IV) wherein Z is a nucleus having six reactive sites, D is a linear or branched chain extender having two reactive sites and T is a chain termination or suitable terminal function. ##STR1##
Utilization of a hyperbranched dendritic macromolecule in accordance with the present invention as toughening agent allows the toughness of high performance thermosetting compositions to be increased without affecting the thermomechanical properties and the processability. A relatively high molecular weight toughening agent will facilitate the control of the phase separation process and increase its efficiency as toughener. However, high molecular weights in general imply a high viscosity which is to be avoided in favor of a low or medium viscosity. Hyperbranched dendritic macromolecules used as toughening agents in accordance with the present invention satisfy the requirements of low viscosity and high molecular weight. Hyperbranched dendritic polymers exhibit lower viscosities than linear or starbranched polymers of comparable molecular weight. The mechanical properties of a hyperbranched dendritic macromolecule will substantially be determined by the interior architecture of said macromolecule and the chemical structure of the outer or shell structure, such as terminal functions or sites, chain termination, functionalization and the like, will define for instance phase separation processes. The inner and especially the outer structure will, consequently, normally influence and/or determine the mechanical properties of a molded and cured or semi-cured thermosetting material.
Hyperbranched dendritic macromolecules exhibit a spherical structure resembling that of particles. There is, however, no singularity in mechanical properties at the interface of said macromolecules and surrounding resin or resin composition (the so called resin matrix) as with various particles. Isolated hyperbranched dendritic macromolecules have in the case of phase separation, residual miscibility in said resin or resin composition, which due to the relatively high molecular weight, the unique molecular structure and large number of reactive sites will increases the toughness of said molded and cured or semi-cured thermosetting material. Increased toughness, due to impacting forces being effectively distributed within the hyperbranched structure of said macromolecules, is also obtained using said hyperbranched dendritic macromolecules as toughening agent. Hyperbranched dendritic macromolecules do not or only moderately increase the viscosity and are of a small diameter despite the relatively high molecular weight. The macromolecules do not as for instance pre-shaped particles impart the processability of the system. The obtained toughening effect will contrary to the interleaf technique be distributed homogeneously in all levels of the material.
The functionality and polarity of a hyperbranched dendritic macromolecule, used as toughening agent according to the present invention, can as previously disclosed be adapted to any resin system to provide appropriate reactive functions or sites as well as phase separation properties. Said macromolecules are therefore not as sensitive to different matrix chemistry as for instance polyetherimide modifiers requiring a modification of the entire resin chemistry. The relatively high molecular weight of said hyperbranched dendritic macromolecule makes for instance the control of the phase separation easier.
The thermosetting composition of the present invention, which is cured to produce the product of this invention, includes as one component, a curable and moldable thermosetting compound or resin. Among the thermosets within the contemplation of the present invention are thermosetting resins or compounds such as epoxy resins, polyesters, allyl resins non-etherated amino resins, phenolics, silicone resins, polyimides, furan resins polyurethane, and polyisocyanates.
Epoxy resins are monomers or prepolymers that further react with curing agents to yield high performance thermosetting molded products. Widely used epoxy resins are linear or branched aliphatic and aromatic epoxides and epoxy resins, such as polyglycidyl ethers derived from for instance bisphenol A or F and epichlorohydrin, ester epoxides or epoxy resins, epoxidized cresol or phenol novolac resins. Epoxies are in general bisphenol A or F type novolacs and derivative thereof. Cycloaliphatic epoxy resins are a further group of epoxies renowned for their high-performance properties in coating applications. Thermoset molding epoxy compositions are multicomponent mixtures based on said epoxides or epoxy resins, hardeners and various fillers and reinforcements. The exact nature of the compounds or resins is usually dictated by the application and the molding procedure to be used. Moldable epoxides and epoxy resins are formulated to meet stringent requirements regarding flow, reactivity, electrical properties, humidity and thermal resistance. The resin system may be formulated to cure at either room temperature or at elevated temperatures. The good adhesive properties and the low shrinkage on cure of epoxies and epoxy resins normally requires incorporation of an release agent into the molding formulation. Epoxy resins require a hardener, accelerator or crosslinking resin such as amines, amides, polyamines, polyamides, dicyandiamides, Lewis acids; isocyanates, functional urethanes or polyurethanes, acid anhydrides, phenol-formaldehyde resins and/or amino resins. Cycloaliphatic epoxy resins are most easily cured by acids, amine curing agents have poor effect due to low reactivity and possible aminolysis of esterlinkages at the high curing temperatures required to gel and vitrify the product. Cationically cured, such as radiation cured, cycloaliphatic epoxide coating formulations wherein the curing agent is for instance an iodonium salt have been developed and reported to yield very high solids coatings, which of course not is encompassed by the appended claims. Such formulations are reported and disclosed in "Alkoxy-Substituted Diaryliodonium Salt Cationic Photoinitiators" by J. V. Crivello and J. L. Lee, published in J. Pol. Sc. 1989, pp 3951-3968, Product Information "Cyracure" issued by Union Carbide Chemicals and Plastics Co. Inc., and in U.S. Pat. No. 4,342,673, Wolfroy 1982. This is, furthermore, reported in WO 93/17060 (U.S. Pat. No. 5,418,301) wherein a hyperbranched dendritic polyester is employed as flexibilizer in a coating formulation including a cycloaliphatic diepoxy and an iodonium salt.
Polyurethanes are formed through an addition reaction between isocyanates or polyisocyanates and alcohols, polyalcohols or phenols.
Amino resins are thermosetting polymers made by combining an aldehyde with a compound containing an amino group. The two most important types of amino resins used in molding compositions are methylolmelamines and methylolureas. One of the most important applications for methylolmelamines and methylolureas are decorative and industrial laminates. Etherified amino resins, for instance methylated, such as hexamethoxymethylmelamine, and butylated melamines and ureas are important as amino crosslinkers for curing of coating compositions, such as paint films.
Thermosetting polyesters can be produced from such compounds as phthalic or maleic anhydrides and polyfunctional alcohols. Catalyzation is generally achieved by the use of free radical producing peroxides. Unsaturated diallylphthalate and/or vinyl toluene monomers are frequently added to promote flow and to extend flow life. Crosslinking occurs through free radical initiated polymerization of for instance maleic or fumaric double bonds or by copolymerization with added unsaturated monomers. Since no volatile products are evolved during cure, these materials can be fabricated by low pressure molding with very short molding cycles.
Allyl resins used in the manufacture of thermosetting molded products are either the orthophthalate or the isophthalate prepolymer. The diallyl phthalate monomer is an ester produced by the esterification process involving a reaction between an acid (o-phthalic anhydride or isophthalic acid) and an alcohol (allyl alcohol). The monomer is capable of being crosslinked and polymerized in the presence of for instance peroxide catalysts. Due to their outstanding property profile and the ability to retain properties even then subjected to severe environmental conditions involving elevated temperatures, high ambient humidity under load over time has led to their use applications wherein unfailing performance is essential.
A further and widely used group of unsaturated resins or compounds are vinyl esters which can be exemplified by reaction products of epoxies and acrylic or methacrylic acid. Vinyl esters have properties in-between unsaturated ester/polyesters and epoxy resins. They usually combine good mechanical properties with excellent chemical resistance.
Thermosetting polyimides are substantially derived from polyamic acids by either chemical or thermal treatment over a temperature range from room temperature to 300.degree. C. Conversion of bismaleimide to polymeric systems require copolymerization with amines or nucleophilic monomers via a Michael addition reaction or with olefinic or acetylenic monomers.
Phenolic based thermosetting molded products are, by far the most widely known and used of all the thermosets. Over the last nine decades, since Dr. Baekeland's successful reaction between phenol and formaldehyde (Bakelite), phenolics have found applications in chemical, industrial and military areas due to the inherent property profile, diverse range of reinforcements, low cost and extreme ease of molding in most commercial thermosetting molding processes. Phenols react with aldehydes to give condensation products if there are free positions on the benzene ring, ortho and para to the hydroxyl group and formaldehyde is by far the most reactive and commonly used. The reaction is always catalyzed, either by acids or by bases. The nature of the product is greatly dependent on the type of catalyst and the mole ratio of the reactants. There are four major reactions in the phenolic resin chemistry, with the novolac (two stage) and the resole (single stage) being the two most widely used for the production of thermosetting molded products.
Silicone molding resins and compounds utilize a base resin that is the result of reacting silicone with methylchloride to produce methyichlorosilanes. A typical molding composition will contain 20-25% resin (phenyl or methyl siloxanes, 75% filler (mixtures of glass fibers and fused silica), lead based catalysts and pigments and lubricants that promotes flow and good release properties.
Furan resins are the commonly used designation for resins based on furfural, furan, tetrahydrofuran and furfurol (furfuryl alcohol). The furan resins include compounds such as phenol-furfural resins, urea modified furfurol resins, phenol modified furfurol resins, formaldehyde modified furfurol resins, unmodified furfurol resins, halofurans, alkoxyfurans, furfuryl esters, furfuryl ethers and furfural acetates. The major application areas include metal casting cores and molds.
The thermosetting product of the present invention, a partially or fully cured thermosetting material, is produced in a process which comprises subjecting a thermosetting composition to a molding and curing process at a temperature of 0-400.degree. C., such as 10-350.degree. C. or 25-150.degree. C. The thermosetting composition comprises at least (a)70-99% by weight, preferably 80-99% by weight, of at least one thermosetting resin or compound selected from the group consisting of, an epoxy resin, a saturated polyester, an unsaturated polyester, an allyl resin, a polyimide, a polyetherimide, a bismaleimide, a phenol-formaldehyde resin, a non-etherified amino resin, a silicone resin, a phenolic resin, a furan resin, a polyisocyanate, a polyurethane having at least one hydroxyl, carboxyl or cyano group and a polyurethane having at least one hydroxyl, carboxyl or cyano group; and (b) 1-30% by weight, preferably 1-20% by weight, of at least one toughening agent having at least one primary or secondary functional group, said functional group formed by chain branching, chain termination or functionalization, forming a reaction product with said component (a) by means of covalent bonding, said toughening agent comprising at least one hyperbranched dendritic macromolecule formed of ester units, optionally in combination with ether units, said hyperbranched dendritic macromolecule comprising a monomeric or polymeric nucleus having at least one reactive epoxide, hydroxyl, carboxyl, anhydride group or combination thereof, 1 to 20 generations of at least one monomeric or polymeric branching chain extender, said branching chain extender containing at least three reactive groups, of which at least one is a hydroxyl group and at least one is a carboxyl or anhydride group, bonded to said nucleus and, optionally, at least one generation of at least one spacing chain extender, one chain stopper or both. The percentages of components (a) and (b), are based on the total weight of the thermosetting composition.
Chain termination of said macromolecule is preferably obtained by addition of at least one monomeric or polymeric chain stopper to said hyperbranched dendritic macromolecule. A chain stopper is then advantageously selected from the group consisting of an aliphatic or cycloaliphatic saturated or unsaturated monofunctional carboxylic acid or anhydride having 1-24 carbon atoms, an, aromatic monofunctional carboxylic acid or anhydride, a diisocyanate, an oligomer or an adduct thereof, a glycidyl ester of a monofunctional carboxylic or anhydride having 1-24 carbon atoms, a glycidyl ether of a monofunctional alcohol with 1-24 carbon atoms, an adduct of an aliphatic or cycloaliphatic saturated or unsaturated mono, di, tri or polyfunctional carboxylic acid or anhydride having 1-24 carbon atoms, an adduct of an aromatic mono, di, tri or polyfunctional carboxylic acid or anhydride, an epoxide of an unsaturated monocarboxylic acid or corresponding triglyceride, which acid has 3-24 carbon atoms and an amino acid. Suitable chain stoppers are for instance formic acid, acetic acid, propionic acid, butanoic acid, hexanoic acid, acrylic acid, methacrylic acid, crotonic acid, lauric acid, linseed fatty acid, soybean fatty acid, tall oil fatty acid, dehydrated castor fatty acid, crotonic acid, capric acid, caprylic acid, acrylic acid, methacrylic acid, benzoic acid, para-tert.butylbenzoic acid, abietic acid, sorbic acid, 1-chloro-2,3-epoxypropane, 1,4-dichloro-2,3-epoxybutane, epoxidized soybean fatty acid, trimethylolpropane diallyl ether maleate, toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, hexamethylene diisocyanate, phenyl isocyanate and/or isophorone diisocyanate.
It is emphasized that the above-discussed chain stopper includes compounds with or without functional groups. In preferred embodiments where the chain stopper includes functional groups it is these functional groups which serve as the primary or secondary group which covalently bonds to produce a reaction product between component (a) and the toughening agent.
A functionalization of said hyperbranched dendritic macromolecule (with or without chain termination) is preferably a nucleophilic addition, an oxidation, an epoxidation using an epihalohydrin such as epichlorohydrin, an allylation using an allylhalide such as allylchloride and/or allylbromide, or a combination thereof. A suitable nucleophilic addition is for instance a Michael addition of at least one unsaturated anhydride, such as maleic anhydride. Oxidation is preferably performed by means of an oxidizing agent. Preferred oxidizing agents include peroxy acids or anhydrides and haloperoxy acids or anhydrides, such as peroxyformic acid, peroxyacetic acid, peroxybenzoic acid, m-chloroperoxybenzoic acid, trifluoroperoxyacetic acid or mixtures thereof, or therewith. Oxidation may thus result in, for instance, primary and/or secondary epoxide groups.
To summarize, functionalization refers to addition or formation of functional groups and/or transformation of one type of functional groups into another type. Functionalization includes nucleophilic addition, such as Micheal addition, of compounds having functional groups, epoxidation/oxidization of hydroxyl groups, epoxidation of alkenyl groups, allylation of hydroxyl groups, conversion of an epoxide group to an acrylate or methacrylate group, decomposition of acetals and ketals, grafting and the like.
The nucleus of said hyperbranched dendritic macromolecule, is in preferred embodiments selected from the group consisting of a mono, di, tri or polyfunctional alcohol, a reaction product between a mono, di, tri or polyfunctional alcohol and ethylene oxide, propylene oxide, butylene oxide, phenylethylene oxide or combinations thereof, a mono, di, tri or polyfunctional epoxide, a mono, di, tri or polyfunctional carboxylic acid or an anhydride, a hydroxyfunctional carboxylic acid or anhydride.
Said mono, di, tri or polyfunctional alcohols can be exemplified by 5-ethyl-5-hydroxymethyl-1,3-dioxane, 5,5-dihydroxymethyl-1,3-dioxane, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, pentanediol, neopentyl glycol, 1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, cyclohexanedimethanol, trimethylolpropane, trimethylolethane, glycerol, erythritol, anhydroennea-heptitol, ditrimethylolpropane, ditrimethylolethane, pentaerythritol, methyl-glucoside, dipentaerythritol, tripentaerythritol, glucose, sorbitol, ethoxylated trimethylolethane, propoxylated trimethylolethane, ethoxylated trimethylolpropane, propoxylated trimethylolpropane, ethoxylated pentaerythritol or propoxylated pentaerythritol.
Said mono, di, tri or polyfunctional epoxide is suitably exemplified by the group consisting of a glycidyl ester of a monofunctional carboxylic acid having 1-24 carbon atoms, a glycidyl ether of a monofunctional alcohol having 1-24 carbon atoms, a glycidyl ether of a di, tri or polyfunctional alcohol, a mono, di or triglycidyl substituted isocyanurate, a glycidyl ether of a condensation product between at least one phenol and at least one aldehyde or an oligomer of such a condensation product, a glycidyl ether of a condensation product between at least one phenol and at least one ketone or an oligomer of such a condensation product, and a glycidyl ether of a reaction product between at least one mono, di, tri or polyfunctional alcohol and ethylene, propylene, butylene and/or phenylethylene oxide.
A branching chain extender of said hyperbranched dendritic macromolecule, is in various preferred embodiments selected from the group consisting of an aliphatic di, tri or polyhydroxyfunctional saturated or unsaturated monocarboxylic acid or anhydride, a cycloaliphatic di, tri or polyhydroxyfunctional saturated or unsaturated monocarboxylic acid or anhydride, an aromatic di, tri or polyhydroxyfunctional monocarboxylic acid or anhydride, an aliphatic monohydroxyfunctional saturated or unsaturated di, tri or polycarboxylic acid or anhydride, a cycloaliphatic monohydroxyfunctional saturated or unsaturated di, tri or polycarboxylic acid or anhydride, an aromatic monohydroxyfunctional di, tri or polycarboxylic acid or anhydride, and an ester prepared from two or more of said hydroxyfunctional carboxylic acids or anhydrides. Said branching chain extenders are for example compounds such as 2,2-dimethylolpropionic acid, .alpha.,.alpha.-bis(hydroxymethyl)butyric acid, .alpha.,.alpha.,.alpha.-tris(hydroxymethyl)acetic acid, .alpha.,.alpha.-bis(hydroxymethyl)valeric acid, .alpha.,.alpha.-bis(hydroxy)propionic acid, 3,5-dihydroxybenzoic acid, .alpha.,.beta.-dihydroxypropionic acid, heptonic acid, citric acid, d- or l-tartaric acid, dihydroxymaloic acid and/or d-gluconic acid.
An optional spacing chain extender of said hyperbranched dendritic macromolecule is advantageously selected from the group consisting of an aliphatic monohydroxyfunctional monocarboxylic acid or anhydride, a cycloaliphatic monohydroxyfunctional monocarboxylic acid or anhydride, an aromatic monohydroxyfunctional monocarboxylic acid or anhydride, and a lactone (an inner ether of a monohydoxyfunctional monocarboxylic acid) and can be exemplified by hydroxyacetic acid, hydroxyvaleric acid, hydroxypropionic acid, hydroxypivalic acid, glycolide, .delta.-valerolactone, .beta.-propiolactone or .epsilon.-caprolactone.
The thermosetting composition comprises, in a number of preferred embodiments, and in addition to said thermosetting resin or compound and toughening agent at least one component selected from the group consisting of a reinforcing material, a curing agent, a catalyst, an inhibitor, a stabilizer, a lubricant, a mold release agent, a filler and a pigment.
It will be understood, of course, that said functional groups and/or included curing agents, accelerators or curing resins are combined in such a way that proper chemical reactions are obtained resulting in covalent bonding between component (a) and the toughening agent either directly or through intermediation by a curing agent or resin. Improper combinations often lead insufficient formation of covalent bonds, hence resulting in for instance macroscopic phase separation which is exemplified by embodiment examples 35 and 36.
Said reinforcing material is preferably a material selected from the group consisting of glass fibers or particles, carbon fibers or particles, graphite fibers or particles, mineral fibers or particles, aramide fibers or particles and organic fibers or particles, such as cellulosic fibers or particles. Said glass fibers or glass particles are suitably surface treated with at least one silane, such as methacrylsilane or aminosilane. Said reinforcing material is furthermore and advantageously a fibrous material employed in form of a roll, a sheet, a web, a cloth, threads and cuttings.
The thermosetting product of the present invention is preferably employed in a molding process to produce useful products. This molding process may involve press molding, pour molding, injection molding, gas assisted injection molding, structural injection molding, rotary molding, blow molding, vacuum molding, extrusion, filament winding, die forming, such as extrusion, rotary molding, gravity molding, blow molding, casting and pour molding and includes optionally resin immersion, resin infusion or resin transfer. The molding process comprises suitably spraying a thermosetting product in accordance with the present invention onto or into a pre-shaped mold. Further embodiments of the molding process includes lamination and/or prepreging.
The molding process yields, in addition to other molded articles, a laminated or sheet molded sandwich structure, in form of an overlay, an underlay or an intermediate layer, with at least one additional thermosetting composition, at least one metal or at least one cellulose based substrate.
The thermosetting product of the present invention is advantageously a prepreg obtained by partial curing, to a B-stage, of a roll, a sheet, a web, a cloth, threads or cuttings selected from the group consisting of glass fibers, carbon fibers, graphite fibers, mineral fibers, aramide fibers and organic fibers, which fibers are impregnated with the thermosetting composition of the present invention. These embodiments can be further processed to yield a decorative or industrial laminate, whereby two or more prepregs are laminated together under heat and pressure.
The thermosetting product is suitably a finished or semi-finished decorative or industrial laminate and/or is a finished or semi-finished product selected from the group consisting of aeronautic goods and articles, nautic goods and articles, chemicals and chemical goods and articles, automotive goods and articles, sporting goods and articles, leisure and commodity goods and articles, and electric and electronic goods and articles. All of said materials, goods and articles can optionally have at least one metal plated or metal clad surface.
Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The following preferred specific embodiments are, therefore, to be construed as merely illustrative and not limitative of the remainder of the disclosure in any way whatsoever.
Embodiment Examples 1-37 disclose:
Examples 1 and 2 relate to preparation of hyperbranched dendritic polyester macromolecules used as toughening agent.
Examples 3-8 and 22-24 relate to various chain termination and/or functionalization of the hyperbranched dendritic macromolecules of Examples 1 and 2.
Examples 9-15 relate to preparation of epoxide resin matrices wherein the macromolecules of Examples 3-8 are included.
Example 16 is a comparative example wherein a resin matrix outside the scope of the invention is prepared.
Example 17 relate to molding of the resin matrices of Examples 9-16.
Examples 18-21 relate to evaluations of the molded materials prepared in Example 17.
Table 1 presents results obtained in Examples 18-21 with molded materials based on resin matrices of Examples 9-16.
Example 25 relate to preparation, molding and evaluation of an unsaturated resin matrix wherein the macromolecule of Examples 24 is included.
Example 26 show preparation of a partially chain terminated hyperbranched dendritic polyester from the product of Example 2.
Example 27 relate to epoxidation (functionalization) of the product according to Example 26.
Example 28 relate to composites produced from glass fibers and the resin matrices of Example 12, 27 and 16.
Example 29 relate to composites produced from carbon fibers and the resin matrices of Example 12, 13 and 16.
Examples 30-33 relate to preparation and evaluation of reinforced materials wherein the matrix comprises hyperbranched dendritic polymers.
Example 34 relates to the preparation of a dendritic polyester used in Examples 35 and 36 with a cycloaliphatic diepoxy resin and a bisphenol-F epoxide, respectively, to produce thermosetting compositions which were molded and cured.
Examples 35 and 36 are comparative examples which demonstrate improper combinations which resulted in macroscopic phase separation.
Example 37 relates to the formation a thermosetting cured product of a thermosetting composition which is a reaction product of the toughening agent of Example 9 and a bisphenol-F epoxide.